 /*
 * Copyright (c) 2001, Zoltan Farkas All Rights Reserved.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 */
package org.spf4j.base;

import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
import java.util.concurrent.Callable;

/**
 *
 * @author zoly
 */
@SuppressFBWarnings("NOS_NON_OWNED_SYNCHRONIZATION")
public final class MemorizedCallable<V> implements Callable<V> {

    private volatile V value;
    
    private final Callable<V> callable;
    
    public MemorizedCallable(final Callable<V> callable) {
        this.callable = callable;
        value = null;
    }
       
    @Override
    public V call() throws Exception {
        V result = value;
        if (result == null) {
            synchronized (this) {
                result = value;
                if (result == null) {
                    result = callable.call();
                    value = result;
                }
            }
        }
        return result;
    }
    
    
}
